The present invention relates generally to the preparation of heterocycles containing one or more nitrogen or oxygen heteroatoms, and in particular to the synthesis of such heterocycles utilizing a 1,3-dihalopropene such as 1,3-dichloropropene as 4 starting material.
As further background, heterocyclic compounds such as pyridines, pyrimidines, oxazoles, pyrazoles and quinolines enjoy a wide range of utilities including serving as actives and intermediates in the fields of herbicidal, pesticidal, and medicinal compounds. While many such compounds occur naturally and in the past have been isolated from natural sources, currently, most of the world's supply of such compounds derives from synthetic preparations. Thus, a wide variety of syntheses are known in which one or more acyclic starting materials are reacted either to directly form the heterocycles or to form cyclizable intermediates which can then be converted to the heterocycles.
In light of this background the applicants have undertaken an investigation to discover new and useful routes to the above-mentioned heterocycles which employ readily-available starting materials and which can be conveniently conducted in standard laboratory or commercial equipment. In so doing the applicants have discovered that 1,3-dihalopropenes provide useful 3-carbon fragments for the production of such heterocycles including, for instance, 2,3-substituted pyridines, 2,5-substituted pyridines, pyrimidines, oxazoles, pyrazoles and quinolines.